In a storage cell system, serial circuits each formed by connecting a prescribed number of storage cells in series are connected in parallel to form a storage cell module. Each unit is formed by connecting a prescribed number of storage cell modules in parallel. Outputs of a number of units corresponding to load capacity are linked in parallel and supplied to a load. In this system structure, if a single storage cell fails, and backward current is generated, another storage cell in the same module, another storage cell module or another storage cell unit may sequentially fail.
As a countermeasure, in general, the defect portion is limited by managing each unit in a power conditioning system (PCS). However, the PCS is large and requires a space in comparison with storage cell units. Thus, the PCS is not suitable for the application in a small space or the management based on each module.
Apart from the above method, a fuse is connected to each storage cell to protect it from overcurrent. However, in this method, it is not possible to deal with a rapid increase in current in a storage cell having low impedance.
As described above, in the conventional storage cell system, a PCS is employed as a countermeasure to prevent sequential failures caused in the entire system by the failure of a single storage cell and backward current. However, this countermeasure is insufficient as the PCS is disadvantageous in terms of its size.
Embodiments described herein aim to provide a storage cell system, a storage cell module and a method for operating a storage cell system, capable of certainly preventing sequential failures in the entire system even if a storage cell fails.